1. Field of the Invention
The present invention relates to an apparatus for atomizing large quantities of liquid such as liquid fuels, water, lotions or the like.
2. Prior Art
A variety of liquid atomizers have heretofore been proposed and practiced in the art. One such known atomizer utilizes a pump for ejecting a liquid under pressure through a nozzle. According to another conventional atomizing apparatus, liquid droplets are allowed to fall onto a rotating body and caused upon hitting the latter to be atomized under centrifugal forces. These prior systems, however, require a high-pressure pump or a high-speed motor, are large in size and costly to construct, and cannot achieve a satisfactory degree of liquid atomization for certain applications. There are also known ultrasonic atomizers which incorporate an ultrasonic vibrator for breaking up the liquid into small droplets. One form of such ultrasonic atomizers which incorporate an ultrasonic vibrator for breaking up the liquid into small droplets. One form of such ultrasonic atomizer includes a horn vibrator for amplifying the vibrations from an ultrasonic vibrator up to a level large enough to atomize the liquid supplied to a distal end of the horn. This ultrasonic vibrator is disadvantageous in that the vibration amplifying horn is complex in structure, difficult to machine, expensive to manufacture, and fails to produce liquid droplets of satisfactory diameter. The vibrator necessitates a liquid supplying device such as a pump, and hence is large-sized and cannot be built inexpensively. Another known ultrasonic atomizer comprises an ultrasonic vibrator mounted on the bottom of a liquid container for directly transmitting ultrasonic energy into the liquid to atomize the latter with the ultrasonic energy that reaches the surface of the liquid in the container. Although the ultrasonic atomizing apparatus for direct ultrasonic liquid atomization needs no liquid supplying unit such as a pump and atomizes the liquid into desired droplets, the atomizer consumes a great amount of electric energy for atomization and produces ultrasonic vibrations at quite a high frequency which ranges from 1 MHz to 2 MHz. Such highfrequency ultrasonic vibrations have an increased level of undesirable radiation which has a great potential for causing disturbance of radio waves received by television and radio receivers. Therefore, the atomizer is required to be equipped with a vibrator driving circuit and a noise prevention means, and hence is costly to construct.
U.S. Pat. No. 3,683,212, to Zoltan, patented Aug. 2, 1972, discloses a system for ejecting a train of small liquid droplets through a single orifice in response to pressure increases due to changes in volume of a piezoelectric element to which electric command pulses are applied. The disclosed system can produce a succession of droplets of uniform diameter and is suitable for use in ink jet printers and recorders. The prior droplet ejecting system, however, cannot be used in a liquid fuel burner or a humidifier which atomizes a large amount of liquid, at a rate of 1 to 20 cc/min., into small uniform droplets. More specifically, when the voltage of supplied pulses is increased in order to produce droplets in large quantities, the liquid is broken up into droplets of large diameter. Application of pulses at a higher frequency makes it impossible to eject liquid droplets out of the orifice. The Zoltan system therefore fails to form droplets of small and uniform diameter in large quantities.
In U.S. Pat. No. 3,747,120 to Stemme, patented Jul. 17, 1973, an apparatus for ejecting a succession of small droplets is effective for use in recording devices such as an ink jet printer, but is unable to generate large quantities of atomized liquid as small uniform droplets. The disclosed droplet generator comprises a plurality of superimposed plates having small-diameter channels held in coaxial alignment, a structure which is quite difficult to assemble.
Experiments conducted by the present inventors indicated that the system as shown in U.S. Pat. No. 3,747,120 produced liquid droplets at a rate of about 0.5 cc/min. even when the droplets are of an excessively large diameter, and ejected liquid droplets of smaller diameter at an approximate rate of about 0.1 to 0.2 cc/min. Thus, Zoltan's system has experimentally been proven to fail to eject a large quantity of liquid droplets of small and uniform diameter.